The present invention relates to a photographic projector-printer assembly and, more particularly, to a photographic projector-printer assembly which makes use of a projecting lens having on its object side an optical path-splitting prism as an integral piece.
As well known in the art, there is available a photographic projector-printer assembly in which a negative film held by a negative holder is projected onto a photographic paper through a projecting lens for photographic printing. So far, the measurement of the density distribution, etc. of the negative film by photometry is done by inserting a reflecting mirror in front of (or on the object side of) the projecting lens to guide the light from the negative film to a photometric element, and for printing it is removed out of the optical path. Alternatively, the photometric element is located off and above the optical path at a certain angle for photometric purposes.
However, problems with taking the reflecting mirror in and out of the optical path are that not only is much time needed but there is a drop of printing ability as well, and a problem with spacing the photometric element away from the optical path is that image distortion takes place as the image is seen obliquely, resulting in a drop of measurement accuracy.
Such problems may potentially be solved by locating an optical path-splitting means in front of the projecting lens, but this would give rise to some difficulty when the projecting lens is replaced by one having a different magnification.